Field of the Invention
The present invention relates to a light source control apparatus, such as an image projection apparatus (projector), which uses a light source unit and controls light emissions of multiple light sources included in the light source unit.
Description of the Related Art
Projectors using a light source unit provided with multiple solid light sources, such as light-emitting diodes (LED) and laser diodes (LD), have characteristics including, in comparison to discharge lamps, a higher-luminance output within a shorter period of time, a wider color range and a longer lifetime.
On the other hand, since the solid light sources are semiconductor devices, their luminance decreases at a higher rate of speed when continuously used under high temperature deteriorate. This characteristic makes it necessary for the solid light sources to be always used under a lower temperature compared to the discharge lamps.
Japanese Patent Laid-Open No. 2010-169754 discloses a projector that measures light emission amounts of the solid light sources and performs heat dissipation of the solid light sources when it determines, depending on the measured light emission amount, that the solid light sources have deteriorated, thereby reducing temperature rise of the solid light sources.
Since the solid light sources such as the LEDs and the LDs each have a light emission amount less compared to those of the discharge lamps, many projectors, which require a large light amount, use the light source unit including multiple solid light sources, with all of the multiple light sources being lit.
However, the individual solid light sources have a variation in the lifetime thereamong. This variation in the lifetime causes one of the multiple solid light sources in the light source unit to deteriorate at a higher rate of speed compared to those of the other solid light sources, which may prevent the light source unit from satisfying a required lifetime condition (for example, ten thousand hours immediately prior to a decrease from an initial luminance to 50% thereof). The projector disclosed in Japanese Patent Laid-Open No. 2010-169754 is not intended for lifetime control of the light source unit including such multiple light sources.